Experimental Study On Debonding Dedection Of The Steel-UHPC Composite Slabs Based On PZT

Steel-UHPC light composite bridge deck structure with its light structure,high strength and high local stiffness,has been widely used in the long-span bridge in recent years.While the light composite bridge deck structure contains high percentage of reinforcement and actual casting construction condition may not be good,it will cause the bridge deck initial diseases,such as caking,hollow,which may cause potential safety problems under the action of vehicle load at operation stage.Piezoelectric ceramic materials with high sensitivity and good stability,as well as good economy,which is used in the structure monitoring and damage detection,has been developed rapidiy in recent years.In this paper,the deck debonding problems of the steel-UHPC bridge are investigated,and the experimental research on the damage identification of the component is studied using PZT testing technique.In combination with related research status at home and abroad,this thesis firstly introduces steel-UHPC diseases and some basic knowledge of piezoelectric ceramic,and mainly describes the basic principle of the two PZT testing methods,namely,wave propagation method and impedance dynamic method.According to the related research results,the two methods are very effective monitoring of structural damage,the damage state of development,and approximately determining the damage location.A set of steel-UHPC test specimens with debonding defects(different size and thickness)are designed and casted,and then PZT is sticked in both steel side and UHPC side surface respectively.This thesis firstly conduct the impedance method test.In the analysis of PZT impedance,the RMSD index of various test conditions is calculated to decide the existence of the injury.Experimental analysis shows that piezoelectric ceramic impedance technology can identify the existence of debonding.By using ANSYS piezoelectric module with the transient dynamics analysis method to establish local model test with different thickness of pavement conditions,analysis of the propagation of wave was conducted under the action of different voltages and different frequencies.The results show that wave propagation method can identify the debondings of the composite slab and provide theoretical basis for the following research.In the wave propagation method experimental analysis,the value of the received signal amplitude and the wavelet energy was calculated as characterization value of the wave propagation process.The existence of damage and the degree of damage can be judged by comparison the change of the characteristic value.In order to avoid the limitation of identifying the debondings by using the single feature index,the markov distance method,which considers several indexes,was introduced to determine the separation.Firstly,a sample set embracing 200 samples was established.Then this thesis uses the PSO-Kmeans method to select different amount of samples for clustering analysis,and the clustering center will be the benchmark of Markov distance.The markov distance of the other samples are calculated respectively to compare with datum markov distance.The results show that the Markov distance test can accurately identify the thickness of the debondings and have higher accuracy.